1. Field of the Invention
The present invention relates to a housing for a small pet animal such as a rodent, e.g., a hamster or the like.
2. Description of the Related Art
Recently, hamsters have become popular small pet animals especially for city dwellers since hamsters have a nice appearance and a good behavior and are easy to keep even in a relatively small house such as an apartment house, a town house, and the like.
As a housing for hamsters, a cage-type housing having a main cage portion comprising metal wires and a container-type housing made of formed synthetic resin(plastic) have been commonly used.
Among those common housings, a plastic container-type housing can be made into unique shapes with various colors and can be manufactured efficiently at a lower cost by known thermoforming processes. However, the plastic container-type housing is inferior in the ventilation of the housing because of its airtightness. This sometimes causes the inner environment to become excessively high in temperature and high in humidity for hamsters in summer, for example, which may make the environment unpleasant or even dangerous for hamsters.
Therefore, in a conventional plastic container-type housing, ventilating slits are provided on the walls to improve the ventilation thereof.
However, since rodents such as hamsters, or the like, have a gnawing habit, if the gap of the ventilating slit is too wide, hamsters may gnaw peripheral edges of the slits and escape therethrough. On the otherhand, if the gap of the slit is too narrow or the peripheral edge has a circularly shaped cross-section, the edges of the slits can be prevented from being gnawed by hamsters. However, if the gap of the slit is narrow or the peripheral edge of the opening has round-shaped cross-section, the housing is complicated in structure, Accordingly, a structure of a mold for making the housing becomes complicated and the manufacturing cost of the mold will become expensive, which in turn results in an expensive housing.
Under the circumstances, in a conventional plastic molded housing for a hamster, a number of parallel ventilation slits are formed on a ceiling portion of the housing to which hamsters hardly reach. The gap of each slit is formed wide enough to make the structure simple. This can reduce the manufacturing cost and keep the ventilation of the housing adequate to some degree,
However, in a conventional plastic housing, since ventilation slits or openings are formed on a ceiling portion, the ventilation of the housing is usually inadequate. Therefore, unexpected changes in temperature and/or humidity in the housing can not be prevented. Thus, this housing still has the above mentioned problems that it may be uncomfortable or dangerous to hamsters.
Though ventilation slits formed on side walls of the housing may result in a good ventilation, the above mentioned:problems will arise, i.e., hamsters may gnaw the peripheral edges of the slits, and/or the structure of the housing becomes complicated, resulting in an increased manufacturing cost.